It is well known that ultraviolet rays have a bad influence upon photographic light-sensitive materials. In the photographic light-sensitive materials, light-sensitive photographic emulsions containing silver halide as a chief component are applied to a base having a relatively high electrical insulating property such as a film composed of triacetyl cellulose, polyethylene terephthalate, polystyrene or polycarbonate, or a laminated paper covered with said film. Further, the surface of the photographic light-sensitive materials has a fairly high electrical insulating property. Therefore, when the surface of the photographic light-sensitive material comes in contact with the same or different kind of material during production or treatment of the photographic light-sensitive material, electric charges are generated by friction or separation. This phenomenon is called charging. When accumulation of static electricity by charging reaches a certain limiting value, atmospheric discharge occurs at a particular moment and a discharge spark flys at the same time. When the photographic light-sensitive material is exposed to light by discharging, branched, feathered, spotted or radial images appear after development. Images formed by such a phenomenon are called static marks in the photograhic field. It has been known that distribution of spectral energy of this kind of discharge luminecsence which causes static marks is in a range of 200 nm to 550 nm and particularly the intensity thereof is high in a range of 300 nm to 400 nm, and light energy in this range causes occurrence of static marks. Accordingly, attempts have been made to prevent the occurrence of static marks by shielding ultraviolet rays in a range of 300 and 400 nm by means of ultraviolet ray absorbing agents, as described in, for example, Japanese Patent Publication 10726/75 (corresponding to British Pat. No. 1,378,000 and German Patent No. 2,163,904), Japanese Patent Application (OPI) 26021/76 (corresponding to Belgian Pat. No. 832,793) and French Pat. No. 2,036,679, etc.
Further, excepting light-sensitive materials such as printing sensitive materials which are exposed to a specific light source or roentgen sensitive materials, etc., the conventional photographic light-sensitive materials are sometimes subject to an undesirable influence by ultraviolet rays included in light to be used for exposure. For example, in a black-and-white light-sensitive material, objects to be photographed which have a remarkably large quantity of spectral energy in an ultraviolet region, such as a snow scene, a seashore or the sky, etc. easily form soft tone images. In color light-sensitive materials, since it is desired to record only visible light, the influence of ultraviolet rays is very apparent. For example, when photographing the object which have a comparatively large quantity of spectral energy in the ultraviolet region, such as a distant view, a snow scene or an asphalted load, etc., the resulting color images are rich in cyan color. Further, color reproduction in color images is notably different according to light sources to be used for exposure, such as the sun, a tungsten lamp or a fluorescent lamp, etc. The cause of the difference is a difference of spectral energy in the ultraviolet region of light from these light sources. Namely, color images obtained by exposing to light emitted from a tungsten lamp become more reddish and those obtained by exposing to light emitted from a fluorescent lamp become more bluish than those obtained by exposing to sunlight. Accordingly, in order to obtain color photographic images which have correct color reproduction, it is desirable to prevent ultraviolet rays from reaching the silver halide light-sensitive layer of the color light-sensitive material when photographing. Examples of attempts at such have been described in, for example, Japanese Patent Applications (OPI) No. 56620/76 (corresponding to U.S. Pat. No. 4,045,229) and No. 49029/77 (corresponding to U.S. Pat. No. 4,200,464).
Furthermore, color photographs and, particularly, dye images formed on the light-sensitive emulsion layers by color development easily cause fading or discoloration of color images due to the action of ultraviolet rays. Couplers remaining in the emulsion layers after formation of color images are subject to the action of ultraviolet rays to form undesirable color stains on the finished photographs. This kind of action of ultraviolet rays on color photographs finished by photographic treatment is particularly remarkable with positive prints taken under sunlight containing a large quantity of ultraviolet rays. The fading and the discoloration of color images are easily caused by ultraviolet rays having wavelengths near the visible resion, namely, those having spectral energy in the area of 300 to 400 nm. Examples of useful ultraviolet ray absorbing agents which act in reducing bad influences caused by these types of ultraviolet rays are described in U.S. Pat. Nos. 3,215,530, 3,707,375, 3,705,805, 3,352,681, 3,278,448, 3,253,921, 3,738,837, Japanese Patent Publications 26138/74 and 25337/75, British Patent No. 1,338,265 and Japanese patent application (OPI) 56,620/76, etc.
Hitherto, a number of ultraviolet ray absorbing agents have been proposed for various uses such as the use described above. However, ultraviolet ray absorbing agents used hitherto for silver halide photographic light-sensitive materials are not sufficiently suitable for the above described uses, because they color and form stains due to insufficient stability to ultraviolet rays, heat and humidity. Further, they have inferior compatibility with binders, they diffuse into other layers causing bad influences due to substantial interlayer migration, or the emulsion may be unstable causing separation of crystals. Further, these ultraviolet ray absorbing agents have been frequently used in a surface protective layer of silver halide photographic light-sensitive materials, and when high boiling point organic solvents are used for emulsification, the high boiling point organic solvents soften the layer and substantially deteriorate interlayer adhesion or antiadhesive property. In order to prevent such problems, it is necessary to use a large amount of gelatine or to provide a gelatine protective layer on the layer. This results in thickening the layer containing the ultraviolet ray absorbing agent.
An example of a type of ultraviolet ray absorbing agent which does not have such disadvantages is a polymer ultraviolet ray absorbing agent. However, such agents are insufficient for solving these problems. As a result of earnest studies, the present inventors have found that these problems can be completely solved by using a polymer latex obtained by polymerization of certain kinds of ultraviolet ray absorbing monomers.
There is a process for adding polymer ultraviolet ray absorbing agents in a form of latex to a hydrophilic colloid composition. One such process comprises adding a latex prepared by emulsion polymerization directly to a hydrophilic colloid. Another process comprises dispersing an oleophilic polymer ultraviolet ray absorbing agent obtained by polymerization of ultraviolet ray absorbing monomers in an aqueous solution of gelatine in a form of latex. Such ultraviolet ray absorbing polymer latexes have been described in, for example, U.S. Pat. No. 3,761,272 and 3,745,010, Japanese patent application (OPI) No. 107835/78 and European Pat. No. 27242, etc.
The processes for adding the polymer ultraviolet ray absorbing agents in a form of latex to a hydrophilic colloid composition have many advantages as compared with other processes.
First (1) it is not necessary to use high boiling point organic solvents used hitherto, because hydrophobic materials are in the form of a latex, (2) strength of the film formed from the latex is not deteriorated, (3) it is possible to easily incorporate the ultraviolet ray absorbing agent in a high concentration in the hydrophilic colloid layer, because the latex can contain ultraviolet ray absorbing monomers in a high concentration, and (4) an increase of viscosity is small. Further, (5) other layers are not affected because of complete nonmigration, and (6) separation of the ultraviolet ray absorbing agents in the hydrophilic colloid layer is small and the hydrophilic colloid layer is capable of thinning. Particularly, when the ultraviolet ray absorbing polymer latex is produced by emulsion polymerization a specific method for dispersing is not required and the step of adding the ultraviolet ray absorbing agent to the coating solution can be simplified. However, though the ultraviolet ray absorbing polymer latexes known hitherto have some of the fundamental above described excellent advantages, they have the following problems. Therefore, they can not be practically used if such problems can not be improved.
1. Since the absorption peak of the ultraviolet ray absorbing agent becomes broad, stains are formed or sensitivity of the silver halide emulsion is unnecessary reduced.
2. The absorption characteristic in the 300 to 400 nm range is poor, and the effect of preventing static marks and color reproduction are inferior.
3. Since the ultraviolet ray absorbing agent itself is not sufficiently stable to ultraviolet rays, heat and humidity, it colors and causes stains.
4. Ultraviolet ray absorbing monomers are not suitable for mass production, because they have very low solubility and poor polymerization ability,
3. It is necessary to add a large amount in order to obtain a desired density, because the ultraviolet ray absorbing monomers have a low absorbance.